Insects are the experimental tools in an investigation of factors modifying the kinetics of the sparing effect of dose-fractionation (sdf) and other aspects of sdf mechanisms. Special attention is paid to repair of noncytokinetic injury, as manifested by lifespan changes, decreased sexual competitiveness, or by delay in pupation. Tenebrionid beetles are used for most of the experimental work, but the fleshfly, Sarcophaga bullata, has proven most useful for the pupation delay studies. Attempts are also made to develop insect cell culture into a quantitative radiobiological tool in order to correlate in vivo and in vitro findings; Aedes albopictus are the chief cultured cell system at present.